Assessment of Posterolateral Lumbar Fusion

Abstract

Background:Noninvasive assessment of osseous fusion after spinal fusion surgery is essential for timely diagnosis of patients with symptomatic pseudarthrosis and for evaluation of the performance of spinal fusion procedures. There is, however, no consensus on the definition and assessment of successful posterolateral fusion (PLF) of the lumbar spine. This systematic review aimed to (1) summarize the criteria used for imaging-based fusion assessment after instrumented PLF and (2) evaluate their diagnostic accuracy and reliability.Methods:First, a search of the literature was conducted in November 2018 to identify reproducible criteria for imaging-based fusion assessment after primary instrumented PLF between T10 and S1 in adult patients, and to determine their frequency of use. A second search in July 2021 was directed at primary studies on the diagnostic accuracy (with surgical exploration as the reference) and/or reliability (interobserver and intraobserver agreement) of these criteria. Article selection and data extraction were performed by at least 2 reviewers independently. The methodological quality of validation studies was assessed with the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) and QAREL (Quality Appraisal of Reliability Studies).Results:Of the 187 articles included from the first search, 47% used a classification system and 63% used ≥1 descriptive criterion related to osseous bridging (104 articles), absence of motion (78 articles), and/or absence of static signs of nonunion (39 articles). A great variation in terminology, cutoff values, and assessed anatomical locations was observed. While the use of computed tomography (CT) increased over time, radiographs remained predominant. The second search yielded 11 articles with considerable variation in outcomes and quality concerns. Agreement between imaging-based assessment and surgical exploration with regard to demonstration of fusion ranged between 55% and 80%, while reliability ranged from poor to excellent.Conclusions:None of the available criteria for noninvasive assessment of fusion status after instrumented PLF were demonstrated to have both sufficient accuracy and reliability. Further elaboration and validation of a well-defined systematic CT-based assessment method that allows grading of the intertransverse and interfacet fusion mass at each side of each fusion level and includes signs of nonunion is recommended.Level of Evidence:Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Radiologic Assessment of Interbody Fusion

“…There were 18 different definitions of IF and more than 250 combinations of criteria and classifications that showed very little repetition. These findings are similar to our previous review on posterolateral fusion assessment 30 and confirm the lack of consensus that was described earlier 5,8,31 . Somehow attempts at standardization of IF assessment have mainly focused on imaging modalities 5,7,11,32 , but this review also shows substantial variation exists in fusion criteria/classifications that warrant attention.…”

Efficacy and Outcome Measurement of iFactor/ABM/P-15 in Lumbar Spine Surgery: A Systematic Review

“… 14 The gold standard for assessment of lumbar fusion is surgical exploration; given the invasiveness of this method, several imaging-based surrogates have been established. 23 Aside from plain XRs, the most commonly employed method is the use of CT scan. 24 Several studies have established the agreement between intraoperative exploration and CT findings in posterolateral fusion.…”

“…26 Within studies, there is further variability in definitions of interosseous bridging (such as whether fusion is defined as bridging between transverse processes vs obliteration of the facet joint), which also may lead to uncertainty in comparing graft performance. 23,27 The assessment of fusion in interbody constructs is challenging due to the presence of a potentially radio-opaque interbody device, which often prevents direct visualization of fusion within the implant on plain XRs. Similar to posterolateral fusion, techniques include dynamic radiographs and thin-cut CT scans.…”

Failed back surgery syndrome—terminology, etiology, prevention, evaluation, and management: a narrative review

“…Computed tomography (CT) helps evaluate bony changes in the spinal canal, including facet arthropathy and the condition or position of implants [ 48 ]. Weight-bearing CT can help visualize the postoperative spine and detect minimal instability [ 49 ].…”